the equation of the circle is
(x-h)^2 + (y-k)^2 = r^2
if we replace the terms
(4-5)^2 + (0-(-2))^2 = r^2
Now, we can fin the radius if we solve the previous equation
( - 1 )^2 + ( 2 )^2 =r^2
1 + 4 = r^2
5 = r^2
r = SQRT(5)
Now, since we already know r, we can replace it in the circle equation to obtain the result
so, (x-h)^2 + (y-k)^2 = r^2
iquals to, (x-5)^2 + (y+2)^2 = 5